Whiteman probably won't be in the equation for Utd this season and I expect him to be at Donnie for the duration.
Utd should get both Leonard and Lundstram if deals can be struck as they are different types of midfielders and both would enhance the team/squad. Come next season and with football being very fluid, one of our existing midfielders might have moved on and/or one of Leonard or Lundstram might have gone elsewhere for first team football. Then Whiteman might get his chance at that stage. Alternatively, Whiteman might not progress as much as expected this season and not be up to scratch in a years time. Who knows how it will play itself out?
We should plan for the here and now though and whilst I would like to see Whiteman play for us in the long term, short term he isn't ready yet and we need more options in midfield now.